Electronic timing device



Patented Mar. 16, 1954 ELECTRONIC TIMING DEVICE Robert B. Leighton, Altadena, Calif., assignor to the United States of America as represented by the United States Atomic Energy Commission Application September 26, 1950, Serial No. 186,828

4 Claims.

This invention relates to electronic timing devices and, more particularly, to a method and apparatus for indicating whether or not a plurality of events occur Within a selected interval.

It frequently is necessary to determine whether or not a plurality of events occur substantially spontaneously or scattered, with respect to time. For example, in the art of geophysical prospecting by means of physically spaced charges, it is necessary to observe that the charges detonate within an interval which is small compared to the shock wave travel time to the observation point. Many other occasions arise in the various arts and sciences which require a similar determination of proximity in point of time.

The present invention discloses a simple and reliable electronic device which generates an audio tone having one selected frequency when impressed with a plurality of impulses, all of which occur within a selected time interval and :1

an audio tone of difierent frequency when one or more of the impulses occur after the lapse of the selected time interval.

In a broad sense, the device of this invention in its preferred form comprises a pair of thyratrons both coupled to the source of impulses and so arranged that the first thyratron is firedby the first impulse and locks out the second thyratron for the selected interval so that subsequent impulses occurring in this interval are unable to fire the second thyratron. Any impulse which occurs after the lock-out period fires the second thyratron. Each of the thyratrons are coupled to the control grid of a third thyratron arranged as a relaxation oscillator so iii that the relaxation rate of the third thyratron has aflrst or a second value depending upon whether the first thyratron alone is fired,- or boththe first and second thyratrons are fired. It follows that an audio translator coupled to the relaxation oscillator emits a steady tone of one frequency when all incoming impulses occur within the selected interval, and a different one if one or more impulses occur after the selected interval.

A better understanding of the invention will be afforded by the following specification which includes the accompanying drawing and .a detailed description predicated thereon. In the drawing, a preferred embodiment of the invention is schematically illustrated. The arrangement illustrated utilizes a first thyratron 3 and a second thyratron 5 in a bias control circuit for the relaxation oscillator thyratron I.

Thyratron 3 fires upon the impression of a first impulse on its grid 9. To this end, the thyratron anode is provided with a positive potential by a connection through current limiting resistor M to the positive terminal of anode 1 potential source 24. In order to generate a positive potential for application to the second thyratron, the cathode ll! of tube 3 is connected to a common unipotential conductor, hereinafter for convenience termed ground, through cathl ode resistor l3 and bias potential source [5.

Cathode resistor I3 is shunted with a capacitance IS in order not to degenerate the incoming im pulse applied between grid and cathode and also to prevent overshooting when thyratron 3 fires which might fire thyratron 5. The grid of thyratron 3 is impressed with an initial static nega tive bias through grid leak resistor ii. The thyratron grid and cathode are coupled to input terminals i9 and 24 by means of coupling condenser 23 and ground, respectively. Thus far,

an operable single stage thyratron circuit is described which will fire upon the impression on the grid of a positive pulse of firing magnitude.

In the fired or conducting condition of thy ratron 3, the cathode acquires a positive po tential. This positive potential is impressed across the grid-cathode space of relaxation oscillator thyratron 1 thereby raising the rate of oscillation. Thus it follows that upon the occurrence of a first positive pulse, the audio translator 25 coupled to the relaxa'tion oscillator commences to generate and maintains a distinctive audio tone.

Thyratron 3 remains in the fired condition after being triggered so that in the absence of other effects, the audio tone generated by the third thyratron remains constant.

In order to obtain an indication as to whether or not all succeeding impulses fall within a selected time interval measured from the occurrence of the first impulse, the thyratron 5 and the storage network comprising'condenser 21 and adjustable resistor '29'- are provided. -Thy-.

ratron 5 is provided with anode potential through anode load resistor '3l.- The control or 3 igniting grid 33 is coupled to input terminal [9. The screen grid 35 is connected to storage network 21-29 and through cathode resistor I3 to the negative potential source l5. The control grid is impressed with a static negative bias by source 31.

It is to be noted that, although the firing grids of both thyratrons 3 and are connected to the same negative value, and the same applies to the screen grids, the bias source in the cathode leg of thyratron 3 substantially reduces the effective negative bias on this tube so that tube 3 can fire, but tube 5 has such a. high negative bias that it is locked out for the first impulse. The anode of thyratron 5 is connected to the grid of relaxation oscillator thyratron 1 so that if tube 5 fires, the grid bias of tube I is lowered thereby decreasing the rate of oscillation. The

screen grid potential of tube 5 is substantially I increased in the positive direction by the firing of tube 3, because it is then connected substantially directly to the low end of :resistor 14.

It follows from the foregoing that upon the occurrence of a first positive impulse, thyratron 3 is fired thereby sharply decreasing its anode potential due to theipotential drop through 1TB- sistor M. The negative pulse thus generated is stored in network 221 29 zfor an interval determined by the "values of .21 and 29. The rate of dissipation of the negative charge from grid '35 of tube '5 determines the selected interval before tube 5 can besfired by 'a'positive input impulse. During this interval, thyratron '5 is inactivated and fcannot be .fired. However, in "the event 'a positive impulse arrives after the selected interval, 'tube '5 fires thereby decreasing the potentialon the grid 'of the relaxation oscillator and causing a distinctive (audio tone lower in frequency ito be generated by translator 2 6.

An example of component types "and values which ican be used in :aipractical' embodiment of the invention is shown $011 the drawing. It is to be "understood that the selection of component types and values is representative and for convenience only, and thatma'ny other types of components with suitable values can be used. Further, it "is apparent that other well-known types of tone generators can "be substituted in an obvious manner 'for 'thyratro'n *1 According- 1y, sincethe invention admits of many modifications and variations, it is 'to'be considered limited only by the scope of the appended claims.

What is claimed as new and desirable to be secured by LettersPatent of the United States is:

1. Apparatus for indicating whether or i-not-a plurality of impulsesoccur within aselected time interval comprising a tone generator having a frequency dependent upon the 'magnitude of a potential impressed thereon; first bias generating means "responsive :to a first impulse lfor :generating a first value of positive potential and a negative impulse, and means for electricallyimpressing said-first value of..positive potential on said tone generator; second ,bias generating meansfor generating-anegative going potential; means for impressingsaid negative :going potential on said tone generator; a storage network having a selected period, means for impressing said first bias generating means negative rimpulse on said network .and means electrically conn'ectingsaidnetworkrtoisaid.secondrbias means for inactivating the same .ior the selected interval after activation 0! said first bias agenerai-w ing means by a first inputimpulse,

2. Apparatus for indicating whether or not a plurality of impulses occur within a selected time interval, comprising first potential generating means for generating a positive going potential and a negative going potential in response to the impression thereon of a positive impulse, second potential generating means for generating a negative going potential, means for impressing input impulses on both the first and second means, a tone generator adapted to generate a tone having a frequency dependent on the magnitude of a potential'impresse'd thereon, means for impressing said positive going potential on the tone generator to change the frequency thereof upon the occurrence of a first input, positive impulse, means for impressing the first potential generating means negative going a'potential on the second potential generating meansto inactivate the same for a duration which is 'aiun'cti'on 'of'the parameters of the impressing means, andmeans for coupling the second potentialgenerating "means to the tone generator so that the occurrence of an input positive impulse after said duration causes the generation of a negative going potential by the second potential :generating means to be impressed onsaiditone generator to causeiit 'to operate at a diiierent frequency.

3. Apparatus forindicating-the duration of :00- currencepf a plurality 'of impulses with respect to a selected time interval comprising a relaxation oscillator circuit and "a :first, and a second bias potential generating means, said relaxation oscillator circuit including a grid controlled electron discharge "device, a 'circuit network connecting the electron :discharge device to the first and second bias potential generating means, impulse input :terminals "coupled to said first and second bias:potentialgeneratingmeans, said first bias potential generating means being "adapted to :generate a positive .going 'bias and 'a negative going bias, 'means for impressing said negative going bias -ona storage network, and means 'for connecting said storage network to said second bias potentialgenerating :means whereby a first positive impulse-causes said relaxation oscillator to increase its frequency of oscillation :and an input positive impulse occurring after the negative going bias isdissipated from sa'id network w'causes :the relaxation oscillator .to decrease its frequency of oscillation.

4. combination with 'an 'audiotdne'giineirator, -a:first ithyratron trigger circuit'and aseco'nd thyratron trigger circ'uit :and :at least the second thyratron being of the tetrode type, each for said triggercircuits-having two conditions ofstab'ility, means coupling the igniting grids-"of both of :said thyratrons to input impulse terminals, a resistor in series with the-cathode'of the first thyratron and an adjustable potential storage :network in the-anode circuit of said first thyratron, aresistor serially connected in 'the anode circuit ;of .the second "thyratron, means ifor impressing a static negative bias on :said first thyratron and means for impressing --a static, negative :bias of :larger value-on said second thyratron, *a tone generator including a-grid'controlle'delectron discharge device, aresistor network'connecting the grid of the electron discharge device to the cathode of the first thyratron, and a resistor network connecting the grid of the electron discharge device' to the anode of the :seconddahyratron, :me'ans ielec trically connecting the control grid of the sec 0nd thyratronrtothe cathodeiof theffirst'thyratro'n wherebythenegativebias'isreduced-during a flred condition of the first thyratron, a resistor-capacitor network connecting the second grid of the second thyratron to the anode of the first thyratron, said resistor of the resistor-capacitor net Work being adjustable, whereby said second grid is biassed negatively for an adjustable period after firing of the first thyratron, whereby a first incoming positive impulse fires the first thyratron and increases the frequency of the tone generator and any succeeding positive impulse occurring after the selected period of said network fires the second thyratron and decreases the frequency of the tone generator.

ROBERT BENJAMIN LEIGHTON.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date Sabbah Dec. 29, 1931 Urtel Dec. 9, 1941 Hullegard Sept. '7, 1943 Mumma. June 17, 1947 Montgomery July 13, 1948 Houghton Mar. 4, 1952 MacNeille June 17, 1952 Winter July 15, 1952 

